One way of producing oil and/or gas is to pump fluid through production tubing from a downhole formation to the surface. The fluid may include a mixture of oil, gas and water. There is also a considerable amount of solid particles which are washed out of the downhole formation and are mixed with the fluids. For example, in heavy oil production, it is desirable to produce some of the formation sand. The production of the sand is desirable because it can create or increase the flow passages through the downhole formation. In time, this will allow easier flow of fluids from the formation.
The fluid produced from the downhole formation is usually pumped to the surface with downhole pumps. The downhole pumps can, for example, be progressing cavity pumps, piston pumps, hydraulic pumps, jet pumps, or electric submersible pumps.
The solid particles which are pumped out of the formation sometimes tend to accumulate on the top of the downhole pump and eventually plug the tubing and stop production. When this blockage happens, it is a costly operation to clean the tubing and restart the production in the well. If the downhole pump is powered by a sucker rod, sand can jam the sucker rod string and cause it to break. This leads to expensive operations to get the well back into production.
Solid particles are also a problem in horizontal wells. In the horizontal section of a well, the solid particles will tend to settle in the lower part of the tubing, restricting the flow area of the tubing. This can create a back-pressure on top of the pump and eventually plug the tubing.